1. Field of the Invention
Embodiments of the invention generally relate to magnetoresistive reader structures for sensing data stored on magnetic media and methods of making the structures.
2. Description of the Related Art
In an electronic data storage and retrieval system, a magnetic head typically includes a reader portion having a magnetoresistive (MR) sensor for retrieving magnetically encoded information stored on a magnetic recording medium or disk. The MR sensor includes multiple layers and operates based on a change of resistance of the MR sensor in the presence of a magnetic field. During a read operation, a bias current is passed through the MR sensor. Magnetic flux emanating from a surface of the recording medium causes rotation of a magnetization vector of a sensing or free layer of the MR sensor, which in turn causes the change in resistance of the MR sensor. The change in resistance of the read element is detected by passing a sense current through the read element, and then measuring the change in bias voltage across the read element to generate a read signal. This signal can then be converted and manipulated by an external circuitry as necessary.
A hard magnetic bias structure can be used to stabilize the magnetic movement of the free layer to provide a noise-free response from the MR sensor. In construction of the MR sensor, milling at parallel sides of the layers making up the MR sensor and depositing hard bias layers on both milled sides of the MR sensor accomplishes this stabilization. Further, the milling at both sides defines a track width, while milling through the layers at a back-edge prior to refilling defines a height of the MR sensor relative to an air bearing surface opposite the back-edge.
Prior approaches for defining the height of the MR sensor exist but have disadvantages. Damage at the back-edge of the MR sensor can prevent proper magnetic performance of the MR sensor. Further, shunting around a barrier layer of the MR sensor between the free layer and a pinned layer of the MR sensor can occur at the back edge, thereby introducing noise in the read signal.
Therefore, there exists a need for processes of fabricating magnetoresistive sensors to improve properties of the sensors.